I don't want to read the fanfic stories until I'm done with the series (or give up on it) because of spoilers, but it looks like I found a good list here:
It looks so perfect for me: "...but as a literary work, it's close to perfect. Way, way closer than the original books. Think of it as "what if KA Applegate had taken her time to write the series, made all the characters smarter, and wrote a story that wasn't afraid to make radical choices and break the status quo?" To quote the author, "Visser Three is competent, the Yeerks are moving rapidly, and the Animorphs are actually trying to win, but are inexperienced and unprepared". Every day counts, every advantage is needed, everyone makes mistakes and no one can afford them. "
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https://www.reddit.com/r/Animorphs/comments/559oef/animorphs_fanfiction_recommendations/
It looks so perfect for me: "...but as a literary work, it's close to perfect. Way, way closer than the original books. Think of it as "what if KA Applegate had taken her time to write the series, made all the characters smarter, and wrote a story that wasn't afraid to make radical choices and break the status quo?" To quote the author, "Visser Three is competent, the Yeerks are moving rapidly, and the Animorphs are actually trying to win, but are inexperienced and unprepared". Every day counts, every advantage is needed, everyone makes mistakes and no one can afford them. "